=The Eccentric Strap= is that part of the engine in which the eccentric
revolves, and is attached to link by the eccentric rod. It should be
kept well oiled to secure a free and easy movement to the link.
On reversing engines there are two eccentrics exactly alike, one
connecting with upper end of link, the other with lower end by the
eccentric straps and rods. In this case the eccentric rod that is
moving the valve is the one nearest to the link block. When the lever
is in the center notch the link is also in the center of its travel.
In this case, both of the eccentric rods move an equal distance and
the link vibrates back and forth, but as the block is in the center
it gives no motion to the valve, and as the valve, having sufficient
lap, covers both ports when the lever is in this position prevents the
ingress of steam to the cylinder, consequently no motion.